Subterranean drilling systems can employ various tools that require electrical power. In some instances, a drilling system includes a power generation unit. Fluid, such as drilling fluid, may flow through a turbine of the power generation unit, thereby producing rotation of a shaft, which may be converted into electrical power (e.g., the power generation unit may drive an alternator). Bearing apparatuses (e.g., thrust, radial, tapered, and other types of bearings) also may be operably coupled to the shaft and may assist in maintaining the shaft in a substantially stationary lateral and/or axial position, for instance, relative to a housing, while allowing the shaft to rotate.
A typical bearing apparatus includes a stator that does not rotate and a rotor that is attached to the shaft and rotates with the shaft. The operational lifetime of the bearing apparatuses often determines the useful life of the power generation unit as well as of the subterranean drilling system. Therefore, manufacturers and users of subterranean drilling systems and power generation units continue to seek improved bearing apparatuses to extend the useful life of such bearing apparatuses.